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Unit 5 – 75.00 ptsBackGeneral InstructionsTopics: (1) Nonrenewable Energy Sources and Conservation; (2) Renewable Energy Alternatives.NOTE: Question #7 for Unit 5 is eliminated from the pool and you are not required to answer the question. This does not alter the required 1000 word count and 3 scholarly sources for the unit.Question #1Question #2Question #3Question #4Question #5Question #6Question #7Question #8Question #9Question #10 SaveAssignment Submitted1.Differentiate between a renewable energy source, a nonrenewable energy source, and a clean energy source. Give an example of each. editClick here to edit your answer.Words: 02.Fully describe the method scientists use to determine the net energy available in a fossil fuel deposit.editClick here to edit your answer.Words: 03.What are the three fossil fuels upon which humans rely? From what types of organisms do each of the three fuels specifically come?editClick here to edit your answer.Words: 04.What are oil sands? Describe two problems associated with the extraction of oil sands.editClick here to edit your answer.Words: 05.What is methane hydrate? Describe the possible environmental impacts of extraction.editClick here to edit your answer.Words: 06.Why is the combustion of biomass considered to add no net gain in atmospheric carbon dioxide? When can biomass use as an energy source become nonrenewable?editClick here to edit your answer.Words: 07.Discuss the advantages and disadvantages of growing corn for use in ethanol production.editClick here to edit your answer.Words: 08.Name and describe the three major approaches to using hydropower to generate electricity.editClick here to edit your answer.Words: 09.Differentiate between active solar energy collection and passive solar energy collection. editClick here to edit your answer.Words: 010.What alternative energy source would you want your state to invest most of its budget in? Explain.editClick here to edit your answer.
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15
Nonrenewable
Energy Sources,
Their Impacts, and
Energy Conservation
S
Upon completing this chapter,
A you will be able to:
➤ Identify the energy sources that we use
N
➤ Describe the nature and origin of coal,
F natural gas, and crude oil, and evaluate their extraction and use
➤ Assess concerns over the future depletion of global oil supplies
O
➤ Describe the nature and potential of alternative fossil fuels
R
➤ Outline and assess environmental, political, social, and economic impacts of fossil fuel use, and explore
D
potential solutions
➤ Specify strategies for conserving energy
, and enhancing efficiency
➤ Describe nuclear energy and how we harness it
➤ Assess the benefits and drawbacks of nuclear power, and outline the societal debate over this energy source
B
E
T
H
A
N
Y
1
3
5
3
T
S
The Deepwater Horizon
drilling rig on fire,
April 2010
Essential Environment: The Science Behind the Stories, Fourth Edition, by Jay Withgott and Matthew Laposata.
Published by Benjamin Cummings. Copyright © 2012 by Pearson Education, Inc.
M15_WITH2901_04_SE_C15.indd 325
8/8/11 12:20 AM
CENTR AL C A SE S TUDY
Offshore Drilling and the Deepwater
Horizon Blowout
“This oil spill is the worst environmental disaster America has ever faced.”
—U.S. President Barack Obama, 2010
“The Deepwater Horizon incident is a direct consequence of our global addiction to oil.
. . . If this isn’t a call to green power, I don’t know what is.”
S
A
N
t began with a spectacular and deadly explosion
that killed 11 people far out to sea. It
F And its consequences will stretch on for
captivated a horrified nation for three months.
O
years. The collapse of British Petroleum’s Deepwater
Horizon drilling rig and the resulting
R
oil spill from its Macondo well in the Gulf of Mexico polluted water, beaches, and marshes;
D
shut down fisheries; ruined tourism; and killed countless animals. The oil contaminated over
,
—University of Georgia Researcher Dr. Mandy Joye, 2010
I
1,050 km (650 mi) of coastline in Louisiana, Mississippi, Alabama, and Florida (FIGURE 15.1). Ultimately, it raised the question of what costs we are prepared to accept in order to continue
relying on fossil fuel energy.
B
E
T
H
AMISSISSIPPI
ALABAMA
N
LOUISIANA
Y
The catastrophe in the
and captured oiled birds and
Gulf began on April 20, 2010,
wildlife to clean and release.
when a large bubble of natuThe work was hot, dirty, and
ral gas rose through the drill
difficult, and the scale of the
pipe at the Macondo well bejob seemed overwhelming.
TEXAS
ing drilled by British PetroBy the time BP engineers
leum (BP) a mile underwater.
finally got the well sealed 86
FLORIDA
The gas bubble shot past a
days later, roughly 4.9 million
Area
1of oil spill
malfunctioning blowout prebarrels (230 million gallons)
venter and set off a fiery
of crude oil had entered the
Gulf 3
Of Mexico
MEXICO
explosion atop the Deepwater
Gulf, creating the largest ac5
Horizon platform, which sank
cidental oil spill in history. As
3
two days later. The stage had
oil washed ashore, it coated
been set by a series of setbeaches and salt marshes,
T
backs that put the drilling behind schedule and led
killing birds, turtles, crabs, fish, and plants, and spoiling
S
BP and its contractors to cut corners while governtourism for an entire summer. Thousands of fisherment regulators looked the other way.
men were thrown out of work as some of the nation’s
As oil spewed from the seafloor at a rate of 2,000
most productive fisheries were shut down.
gallons every minute, response efforts swung into acMany Americans who watched news coverage of
tion. Dozens of ships and boats tried to corral the risthe spill day after day felt shock and outrage. Indeed,
ing oil at the surface and burn off what they could.
the Gulf oil spill resulted from careless missteps by a
Planes and helicopters dumped chemical dispersants
corporation and its contractors under weak oversight
from the air. Thousands of people in protective Tyvek
from the federal government. However, the spill is
suits walked the beaches and spread booms to soak
perhaps best viewed not as a single isolated instance
up oil. Teams surveyed marshes for contamination
of bad practice or misfortune, but as a by-product of
Essential Environment: The Science Behind the Stories, Fourth Edition, by Jay Withgott and Matthew Laposata.
Published by Benjamin Cummings. Copyright © 2012 by Pearson Education, Inc.
M15_WITH2901_04_SE_C15.indd 326
8/8/11 12:20 AM
SOURCES OF ENERGY
GEORGIA
Tallahassee
Humanity has devised many ways to harness the renewable
and nonrenewable forms of energy available on our planet
(TABLE 15.1). We use these energy sources to heat and light
our homes; power our machinery; fuel our vehicles; produce
plastics, pharmaceuticals, and synthetic fibers; and provide
the comforts and conveniences to which we’ve grown accustomed in the industrial age.
FLORIDA
LOUISIANA
New
Orleans
Tampa
Macondo Well
(site of Deepwater
Horizon blowout)
Oil on shoreline
Very light oiling
Medium oiling
Heavy oiling
Light oiling
Oil on water surface
1-10 days
10-30 days
More than 30 days
(a) Extent of the oil spill
(b) Workers scrub oil from a Louisiana beach
FIGURE 15.1  Oil from the Macondo well blowout spread over
thousands of square miles of the Gulf of Mexico (a) in the spring and
summer of 2010. Darker areas indicate more days with signs of oil
at the surface. Thousands of volunteers, government officials, and
citizens paid by British Petroleum assisted (b) in the vast cleanup
effort. Source (a): National Geographic and NOAA.
our society’s insatiable appetite for petroleum, driven
largely by our reliance on automobiles. Our thirst for
fossil fuels has led the oil industry to drill farther and
farther out to sea, in search of larger and more profitable untapped deposits. In many cases it has found
them, but the farther it moves offshore, the more risks
build for major accidents that are hard to control.
Until we reduce our dependence on oil and shift
to clean and renewable energy sources, we will suffer pollution in the sea and in the air, climate change
and health impacts from fossil fuel combustion, and
economic uncertainty from reliance on foreign sources
of oil. Every once in a while, some drastic event makes
these costs painfully apparent. The Deepwater Horizon spill was not the first such event, and it will likely
not be the last. ■
We use a variety of energy sources
Most of Earth’s energy comes from the sun. We can harness energy from the sun’s radiation directly by using solar
power technologies. Solar radiation also helps drive wind
S and the water cycle, enabling us to harness wind power and
power. And of course, sunlight drives phoA hydroelectric
tosynthesis (p. 30) and the growth of plants, from which
N we take wood and other biomass as a fuel source. Finally,
F when plants die, some may impart their stored chemical energy to fossil fuels , highly combustible substances formed
O from the remains of organisms from past geologic ages. The
R three fossil fuels we use widely today are oil, coal, and natural gas.
D Fossil fuels provide most of the energy that our econ, omy buys, sells, and consumes, because their high energy
content makes them efficient to ship, store, and burn. We
use these fuels for transportation, heating, and cooking, and
B also to generate electricity, a secondary form of energy that
is easier to transfer over long distances and apply to a variety
E of uses. Global consumption of the three main fossil fuels
T
H
A
N
Y
1
3
5
3
T
S
TABLE 15.1 Energy Sources We Use Today
Energy source
Description
Type of energy
Crude oil
Fossil fuel extracted
from ground (liquid)
Nonrenewable
Natural gas
Fossil fuel extracted
from ground (gas)
Nonrenewable
Coal
Fossil fuel extracted
from ground (solid)
Nonrenewable
Nuclear energy
Energy from atomic
nuclei of uranium
Nonrenewable
Biomass energy
Energy stored in
plant matter from
photosynthesis
Renewable
Hydropower
Energy from running
water
Renewable
Solar energy
Energy from sunlight
directly
Renewable
Wind energy
Energy from wind
Renewable
Geothermal
energy
Earth’s internal heat
rising from core
Renewable
Tidal and wave
energy
Energy from tidal
forces and ocean
waves
Renewable
Nonrenewable Energy Sources, Their Impacts, and Energy Conservation
ALABAMA
CHAPTER 15
MISSISSIPPI
Lake
Pontchartrain
327
Essential Environment: The Science Behind the Stories, Fourth Edition, by Jay Withgott and Matthew Laposata.
Published by Benjamin Cummings. Copyright © 2012 by Pearson Education, Inc.
M15_WITH2901_04_SE_C15.indd 327
8/8/11 3:08 PM
Higher EROI ratios mean that we receive more energy from
each unit of energy that we invest. Fossil fuels are widely used
because their EROI ratios have historically been high. However, EROI ratios can change over time. Those for U.S. oil
and natural gas have declined from over 100:1 in the 1940s to
about 5:1 today. This means that we used to be able to gain 100
units of energy for every unit of energy expended, but now we
can gain only five. The EROI ratios for oil and gas declined
because we extracted the easiest deposits first and now must
work harder and harder to extract the remaining amounts.
World fossil fuel consumption
(billion tons of oil equivalent)
4
Oil
3
Coal
2
Natural gas
1
0
1950
1960
1970
1980
Year
1990
2000
2010
FIGURE 15.2  Global consumption of fossil fuels has risen
greatly over the past half century. Oil use rose steeply during the
1960s to overtake coal, and today it remains our leading energy
source. Data from U.S. Energy Information Administration, International
Energy Agency, and BP plc. 2011. Statistical review of world energy 2011.
328
has risen steadily for years and is now at its highest level ever
(FIGURE 15.2).
Energy sources such as sunlight, geothermal energy, and
tidal energy are considered perpetually renewable because
they are readily replenished, and so we can keep using them
without depleting them (pp. 2–3). In contrast, energy sources
such as oil, coal, and natural gas are considered nonrenewable. These nonrenewable fuels result from ongoing natural
processes, but it takes so long for fossil fuels to form that, once
depleted, they cannot be replaced within any time span useful
to our civilization. It takes a thousand years for the biosphere
to generate the amount of organic matter that must be buried
to produce a single day’s worth of fossil fuels for our society.
At our current rate of consumption, we will use up Earth’s accessible store of fossil fuels in just decades to centuries.
Nuclear power as currently harnessed through the fission
of uranium (p. 346) is nonrenewable to the extent that uranium ore is in limited supply. However, we can also reprocess
some uranium and reuse it.
It takes energy to make energy
We do not simply get energy for free. To harness, extract,
process, and deliver the energy we use, we need to invest substantial inputs of energy. For instance, drilling for oil offshore
in the Gulf of Mexico requires the construction of immense
drilling platforms (the Deepwater Horizon cost $560 million)
and extensive infrastructure to extract and transport oil—
all requiring the use of huge amounts of energy. Thus, when
evaluating how much energy a source gives us, it is important
to subtract costs in energy invested from benefits in energy
received. Net energy expresses the difference between energy returned and energy invested:
Net energy = Energy returned – Energy invested
When assessing energy sources, it is useful to use a ratio
often denoted as EROI, which stands for energy returned on
investment. EROI ratios are calculated as follows:
EROI = Energy returned / Energy invested
Energy and its consumption
are unevenly distributed
Most energy sources are localized and unevenly distributed
over Earth’s surface. This is true of oil, coal, and natural gas,
Sand as a result, some regions have substantial reserves of fosAsil fuels whereas others have very few. Nearly two-thirds of
the world’s proven reserves of crude oil lie in the Middle East.
NThe Middle East is also rich in natural gas, but Russia holds
Fmore natural gas than any other country. Russia is also rich
in coal, as is China, but the United States possesses the most
Ocoal of any nation (TABLE 15.2).
R
D TABLE 15.2 Nations with the Largest Proven
Reserves of Fossil Fuels
, Oil
Natural gas
Coal
(% world reserves)
B
E
T
H
A
N
Y
(% world reserves)
(% world reserves)
Saudi Arabia, 17.3
Russia, 23.9
United States, 27.6
Venezuela, 13.8*
Iran, 15.8
Russia, 18.2
Canada, 11.5*
Qatar, 13.5
China, 13.3
Iran, 9.0
Turkmenistan, 4.3
Australia, 8.9
Iraq, 7.5
Saudi Arabia, 4.3
India, 7.0
*Most of Canada’s and Venezuela’s oil reserves occur as oil sands (p.
335), which are included in these figures.
Data are for 2010, from BP plc. 2011. Statistical review of world energy
2011.
Consumption rates across the world are also uneven.
Citizens
of developed regions generally consume far more
1
energy than do those of developing regions. The United States
3has only 4.5% of the world’s population, but it consumes over
520% of the world’s energy. Nations also differ in how they use
Developing nations devote a greater proportion of en3energy.
ergy to subsistence activities, such as growing and preparing
Tfood and heating homes, whereas industrialized countries use
greater proportion for transportation and industry. Because
Saindustrialized
nations rely more on mechanized equipment
and technology, they use more fossil fuels. In the United
States, fossil fuels supply 83% of energy needs.
COAL, NATURAL GAS, AND OIL
The three major fossil fuels on which we rely today are coal,
natural gas, and oil. We will first consider how these fossil fuels are formed, how we locate deposits, how we extract these
resources, and how our society puts them to use. We will then
examine some environmental and social impacts of their use.
Essential Environment: The Science Behind the Stories, Fourth Edition, by Jay Withgott and Matthew Laposata.
Published by Benjamin Cummings. Copyright © 2012 by Pearson Education, Inc.
M15_WITH2901_04_SE_C15.indd 328
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Woody terrestrial
vegetation dies
and falls into
swamp
Phytoplankton,
zooplankton,
and other marine
organisms die
and sink to
sea floor
Ancient swamp
Organic matter
from woody land
plants partly
decomposed
by microbes
under
accumulating
sediments;
kerogen
forms
Ancient ocean
Anaerobic conditions
Organic matter
from soft-bodied
sea life partly
decomposed by
microbes under
accumulating
sediments; some
carbon bonds
broken; kerogen
forms
Heat and pressure
deep underground
alter kerogen
Thermogenic
natural
gas formed
from kerogen
Coal formed
from kerogen
Present day
Crude oil formed
from kerogen
FIGURE 15.3  Fossil fuels begin to form when organisms die
and end up in oxygen-poor conditions, such as when trees fall into
lakes and are buried by sediment, or when phytoplankton and
zooplankton drift to the seafloor and are buried (top diagram). Organic matter that undergoes slow anaerobic decomposition deep
under sediments forms kerogen (middle diagram). Geothermal
heating then acts on kerogen to create crude oil and natural gas
(bottom diagram). Oil and gas come to reside in porous rock layers beneath dense, impervious layers. Coal is formed when plant
matter is compacted so tightly that there is little decomposition.
Nonrenewable Energy Sources, Their Impacts, and Energy Conservation
Fossil fuels form only after organic material is broken down
over millions of years in an anaerobic environment, one with
little or no oxygen. Such environments include the bottoms
of lakes, swamps, and shallow seas. The fossil fuels we burn
today in our vehicles, homes, industries, and power plants
were formed from the tissues of organisms that lived 100–500
million years ago. When organisms were buried quickly in
anaerobic sediments after death, chemical energy in their
tissues became concentrated as the tissues decomposed and
their hydrocarbon compounds (p. 28) were chemically altered amid heat and compression (FIGURE 15.3).
Coal is a hard blackish substance formed from organic
matter (generally woody plant material) that was compressed
under very high pressure, creating dense, solid carbon structures. Coal typically results when water is squeezed out of
the material as pressure and heat increase and time passes,
and when little decomposition takes place because the material cannot be digested or appropriate decomposers are
not present. The proliferation 300–400 million years ago of
swampy environments where organic material was buried has
created coal deposits throughout the world.
Natural gas is a gas consisting primarily of methane
(CH4) and including varying amounts of other volatile hydrocarbons. Oil, or crude oil, is a sludge-like liquid containing a
mix of various hydrocarbon molecules. Oil is also known as
petroleum, although this term is commonly used to refer to
oil and natural gas collectively. Both natural gas and oil have
S formed from organic material (especially dead plankton) that
A drifted down through coastal marine waters millions of years
and was buried in sediments on the ocean floor. This orN ago
ganic material was transformed by time, heat, and pressure
F into today’s natural gas and crude oil.
Two processes give rise to natural gas. Biogenic gas is
O created
at shallow depths by the anaerobic decomposition of
R organic matter by bacteria. An example is the “swamp gas”
D you may smell when stepping into the muck of a swamp. One
source of biogenic natural gas is the decay process in landfills,
, and many landfill operators are now capturing this gas to sell
as fuel (p. 385). Thermogenic gas results from compression and
heat deep underground. Thermogenic gas may form directly,
B along with coal or crude oil, or from coal or oil that is altered by
E heating. Most gas that we extract commercially is thermogenic
and is found above deposits of crude oil or seams of coal, so
T it is often extracted along with those fossil fuels. Indeed, the
H Deepwater Horizon blowout occurred because natural gas acthe oil deposit shot up the well shaft once drilling
A companying
relieved the pressure, and ignited atop the platform.
N Because fossil fuels form only under certain conditions,
occur in isolated deposits. For instance, oil and natural gas
Y they
tend to rise upward through cracks and fissures in porous rock
until meeting a dense impermeable rock layer that traps them.
1 Geologists searching for fossil fuels drill cores and conduct
ground, air, and seismic surveys to map underground rock
3 formations and predict where fossil fuel deposits might lie.
CHAPTER 15
Fossil fuels are indeed fuels
created from “fossils”
329
5
We mine coal and use it
3 to generate electricity
T Coal is the world’s most abundant fossil fuel, and it provides
S 27% of our global primary energy consumption. Once a coal
seam is located, we extract coal from the ground using several methods. For deposits near the surface, we use strip mining, whereas for deposits deep underground, we use subsurface mining (see Figure 11.14, p. 238). Recently, we have begun
mining coal on immense scales in the Appalachian Mountains, essentially scraping off entire mountaintops in a process called mountaintop removal mining (p. 240). (We explored
mining practices and their impacts more fully in Chapter 11.)
People have burned coal to cook food, heat homes, and
fire pottery for thousands of years. Coal-fired steam engines
helped drive the industrial revolution, powering factories,
Essential Environment: The Science Behind the Stories, Fourth Edition, by Jay Withgott and Matthew Laposata.
Published by Benjamin Cummings. Copyright © 2012 by Pearson Education, Inc.
M15_WITH2901_04_SE_C15.indd 329
8/8/11 12:20 AM
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